1. Field of the Invention
The invention relates to the medical arts, and, in particular, to the art of obtaining a cloned cell line expressing functional dopamine receptors and secreting only a single hormone. While many cloning methods have become standard and well known, the instant invention, in addition to including a unique cell line, includes a unique methodology for obtaining the cell line.
2. Brief Description of the Prior Art
Prolactin, also known as luteotropic hormone (LTH) or luteotropin, is a protein hormone produced by the pituitary gland of mammals and acts with other hormones to initiate secretion of milk by mammary glands. The hormone has other functions which are known, but many functions remain unknown. For instance, the function of prolactin in males is not generally understood. It is known that, in humans, prolactin is somewhat similar to human growth hormone.
Adrenocorticotropic hormone (ACTH), also known as corticotropin, is a polypeptide hormone formed in the pituitary gland. ACTH is known to regulate the activity of the outer region (cortex) of the adrenal glands. In mammals, the action of ACTH is limited to the areas of the adrenal cortex in which the glucocorticoid hormones are formed. It is further known that the secretion of ACTH by the pituitary is itself regulated by another polypeptide that is discharged from the hypothalamus in response to impulses transmitted by the nervous system.
Dopamine, also known as hydroxytyramine, is a nitrogen-containing, organic compound formed during the metabolism of the amino acid tyrosine. Dopamine functions as a neurotransmitter. The effects of the deficiency of dopamine is manifest in the form of Parkinson's disease.
Dopamine inhibits prolactin-release from normal anterior pituitary cells. However, the pituitary cell population is heterogeneous, and presently established prolactin-secreting cell lines, as subsequently described, do not express functional dopamine receptors, thereby making the study of control mechanisms difficult.
This problem has persisted in that, until now, all pituitary cell lines have secreted multiple types of hormones, none of which have functional dopamine receptors, thereby rendering the study of hormone secretion difficult.